ozone: evdev: Remove BTN_LEFT from touchscreen probing

This was intended as a fix for some unusual absolute devices that report
having mouse buttons (BTN_LEFT, BTN_MIDDLE, BTN_RIGHT), and aren't
touchpads or tablets.

They are sort of like touchscreens (user interacts directly with
screen), and sort of like tablets (absolute cursor positioning), and
sort of like mice (left/middle/right buttons).

The fact that it wants mouse events rather than touch events makes it
incompatible with the touchscreen code, though, so revert this for now.
We'll have to do something else to support these "absolute mouse"
devices.

BUG=456999
TEST=events_unittests

Review URL: https://codereview.chromium.org/1014853005

Cr-Commit-Position: refs/heads/master@{#321831}

ui/events/ozone/evdev/event_device_info.cc

@@ -343,7 +343,7 @@ EventDeviceInfo::ProbeLegacyAbsoluteDevice() const {
   if (HasKeyEvent(BTN_TOOL_FINGER) && HasKeyEvent(BTN_TOUCH))
     return LegacyAbsoluteDeviceType::LADT_TOUCHPAD;
 
-  if (HasKeyEvent(BTN_TOUCH) || HasKeyEvent(BTN_LEFT))
+  if (HasKeyEvent(BTN_TOUCH))
     return LegacyAbsoluteDeviceType::LADT_TOUCHSCREEN;
 
   return LegacyAbsoluteDeviceType::LADT_NONE;